Trailers are commonly used for transporting cargo. One disadvantage of existing trailers is that most are equipped with a suspension system having an axle that is rigidly attached to the underbody of the trailer, preventing the upward and downward mobility of the trailer. Some trailers are equipped with a ramp to assist with loading and unloading cargo, but typically these ramps are separate components that are either attached to the trailer or are hinged to the rear edge of the trailer. In both configurations, the ramp takes up space on the trailer when the ramp is stowed. Additionally, since the ramps are typically manufactured to be robust to withstand heaving loading conditions, both the hinged ramps and the attached ramps are heavy and difficult to maneuver from the stowed position to the deployed position.
U.S. Pat. No. 8,267,410 to Stutz et al. discloses a trailer having a ramp that is pivotable between a lowered position and a raised position. The suspension assembly has an axle that is pivotally connected to the vehicle, and an actuation device is pivotally connected to the axle. The actuation device is moveable between its extended and retracted lengths, which results in the trailer being lowered or raised from the ground. However, there are several drawbacks of the invention of U.S. Pat. No. 8,267,410, including that a component of the suspension assembly pivots about the side rails of the trailer and protrudes vertically above the bed of the trailer. This configuration can interfere with placement of cargo on the bed of the trailer. Further, the suspension mechanism has a number of plates that cooperate with each other, which causes an increase in the overall width of the trailer (in the direction transverse to the direction of travel).